1. Technical Field
This disclosure generally relates to an image processing method, a recorded matter, a storage medium, an image processing apparatus, an image forming method, an image forming apparatus, an image forming system, and an ink.
2. Description of the Related Art
An ink jet recording apparatus is an image forming apparatus that uses one or more liquid drop spraying heads as recording heads. An ink jet recording apparatus is used, for example, as a printer, a facsimile, a copier, or a multifunction copier having functions of a printer, facsimile, and copier. An ink jet recording apparatus sprays drops of inks or recording liquids from its recording heads onto paper (not limited to a sheet of paper but also refers to any medium, such as an OHP sheet, on which an image can be formed using ink drops or liquid drops, and may also be called a recording medium, recording paper, recording sheet, recording material, medium, or the like), and thereby forms (records or prints) an image on the paper.
Since ink jet recording apparatuses as described above are available at low prices and produce high quality images when used with paper dedicated for ink jet recording apparatuses (ink jet paper), they have rapidly become widespread for personal use. Recently, however, ink jet recording apparatuses are also becoming popular as color recording apparatuses in offices where electrophotographic image forming apparatuses had been the mainstream.
In offices, plain paper is mainly used for printing with an ink jet recording apparatus. Although ink jet paper provides a very high image quality, it is not suitable for daily use because of its high cost.
For this reason, manufacturers are trying to improve fixation and drying characteristics of inks to improve the quality of images printed on plain paper.
Also, a technique called total amount control for limiting the maximum total amount of cyan (C), magenta (M), and yellow (Y) inks per unit area of paper has been devised to prevent overflow (beading) of ink on paper.
For example, patent document 1 discloses an image forming method including a step of controlling the total amount of ink caused to adhere onto paper. In the disclosed image forming method, a color is formed by causing drops of recording liquids of cyan (C), magenta (M), and yellow (Y) to adhere onto a recording medium at substantially the same position. When the total amount of multiple recording liquids for each pixel exceeds a predetermined limit, image data are processed so as to reduce the total amount of multiple recording liquids without changing the substantial proportion of C, M, and Y components in the image to be formed.
[Patent document 1] Japanese Patent Publication No. 2608262
Patent document 2 discloses an image processing apparatus including a total amount control unit for controlling the amounts of color materials. In the disclosed image processing apparatus, record control information for each color component is converted into the amount of color material used after halftone processing, the total amount of color materials for all color components is calculated based on the obtained amount of color material for each color component, and the amounts of color materials are controlled according to the calculated total amount of color materials.
[Patent document 2] Japanese Patent Application Publication No. 2004-009480
Meanwhile, although papers, such as photo paper, coated paper, and OHP sheets, dedicated for ink jet recording apparatuses are expensive, high-quality coated papers for commercial printing (commercial printing papers), such as gloss paper, are relatively inexpensive.
Using such high-quality commercial printing papers enables office users to print documents with an image quality as high as that provided by expensive ink jet papers. More specifically, using such high-quality commercial printing papers for printing with ink jet recording apparatuses makes it possible for office users to create presentation materials, promotional materials, and catalogs with an image quality higher than that provided by plain paper at low costs.
However, plain paper and a commercial printing paper, for example, gloss paper, have significantly different characteristics. On plain paper, liquid drops tend to spread and bleed. On the other hand, on gloss paper, liquid drops do not spread smoothly but clump together.
Therefore, when printing on a commercial printing paper with a conventional ink jet recording apparatus, because of fixation and drying characteristics of inks, ink drops may not adhere onto the paper properly and cause overflow of ink (beading). This problem is making it difficult to print on a commercial printing paper with an ink jet recording apparatus.
One way to solve the above problem is to use inks whose composition has been altered to improve the fixation and drying characteristics. However, using image data processed in the same manner as in the case of printing on plain paper may still cause problems such as overflow of ink (beading), banding, and tone reversal (especially in a part using a black ink) and thereby degrade the image quality.
Such problems may be solved to some extent by reducing the total amount of C, M, and Y inks per unit area when the total amount of C, M, and Y inks exceeds a predetermined limit, as disclosed in patent document 1.
However, when printing on a recording medium on which liquid drops do not spread smoothly but clump together, just controlling the total amount of ink per unit area may not be able to provide sufficient tone and color reproducibility in shaded areas of an image and therefore may not be able to provide a high image quality.